New South Wales police are investigating whether private agents accused of conducting surveillance on environmental activists at Maules Creek may have been acting unlawfully by breaching the state’s licensing laws.

At least two individuals acting under assumed identities are alleged to have attempted to infiltrate community and environmental groups campaigning to stop mining operations at Maules Creek.

Guardian Australia can reveal that neither Tisot nor Groves hold valid security licences or private inquiry licences in NSW. A company linked to Groves, Aquilifer Pty Ltd, which holds the business name “Centre for Intelligence and Risk Management” is also not a valid licence holder.

Following inquiries from Guardian Australia to NSW Police about the licensing, Cameron Smith, the director of the security licensing and enforcement division, said: “I can confirm that none of these entities or individuals hold either security licences or private inquiry licences in New South Wales.”

“We have commenced inquiries into whether there have been any licensing breaches.”

Smith said the police had received a complaint regarding the surveillance following the revelations last week.

Neither Tisot nor Groves have responded to requests for comment about licensing.

The director of C5 Management Solutions, Tyrone Clark, said in response to questions about the licensing requirements: “C5 Management Solutions is a law-abiding corporate citizen. It is the policy of C5 Management Solutions to provide no comment to articles in the media.”

Idemitsu Australia declined to comment on the inquiries. Its chief executive officer, Rod Bridges, has previously said the contract the company held with its security contractors “require that these firms will carry out their services pursuant to the law and all applicable regulations”.

Rick Sarre, a professor of law at the University of South Australia who specialises in private security regulation, said whether or not the company had breached licensing laws would require further investigation into the circumstances of the surveillance.

“The law doesn't require a person to become a private inquiry agent if what they were doing was helping a friend on a one-off basis out to get some information. You have to be carrying out a business,” he said.

Comment has been sought from the alleged undercover agents, the company that contracted them and the mining company Idemitsu.

Allegations of the tactics have prompted a further backlash against the mining companies in the area, which have faced condemnation from community groups and environmental activists.

The coal expansion at Maules Creek is the largest coal mine being constructed in Australia. The expansion will see the demolition of more than 1660 hectares of woodland in the Leard state forest.

A Leard Forest Alliance spokeswoman, Helen War, said the undercover operatives had failed to affect how the groups worked.

“We still really work together, we’re still a really strong community. It’s one of those things that’s kind of rocked the boat a little bit but ultimately hasn’t achieved anything except making that coal company really look questionable,” she said.